hebele
Yes, already in book four there are pieces graded at level 8 by pianosyllabus!
I'm not sure how these books were initially intended to be used in terms of progression speed. The tagline is "Something New Every Lesson" which to me implies that the student wouldn't dwell extensively on any piece. There are 35 pieces in book 4, so if you assign one piece per week or two every second week etc, the book should take roughly a school year with some spare time built in. But a level 8 piece in one week for a fourth year student? The author comments also emphasize style and the importance of playing everything with great musicality and attention to detail. This doesn't quite add up in my brain. Either you stress fast progression and exposure to lots of different composers and styles, akin to the 40 pieces a year challenge, or you make sure the student really polishes the pieces. Expecting both is not realistic in my mind.
I've just kind of assumed that the books were supposed to take around a year each but have not been able to find any confirmation whether that was the author's intent. Anybody knows?
ETA: I also agree on the excessive fingerings, which also in my experience often are anatomically impossible unless you have large hands.